1. Field of the Invention
The present invention relates to a heat pump refrigeration system employing a hermetic motor compressor wherein compressed refrigerant passes over the motor prior to being discharged into the system, and more particularly, to an automatic valved system for providing injection cooling of the compressed refrigerant discharged from the compressor prior to its passage over the motor when the system is operating in the cooling cycle.The valved system further provides for the storage of excess refrigerant when the refrigeration system is operating in the heating cycle.
2. Description of the Prior Art
The present invention is employed in conjunction with a hermetic motor compressor of the type disclosed in U.S. Pat. Nos. 2,967,410--Schulze and 3,006,164--McMillan, both being assigned to the General Electric Company, assignee of the present invention. Both of the above patents disclose means for cooling the motor to maintain its temperature within safe operating limits. The method of motor cooling employed is to pass the high pressure discharge gas from the compressor unit over the motor after this high pressure gas has been cooled to a low enough temperature to remove heat from the motor.
The discharge gas may be cooled by passing it through a superheat removal coil which is connected to the discharge outlet of the compressor unit and extends outside the hermetic casing into the outside ambient and then back to the casing as disclosed in U.S. Pat. No. 3,006,164. Another method used incorporates the injection of refrigerant from the refrigeration system into the casing where it mixes with the discharge gas to cool it prior to its passinng over the motor as disclosed in U.S. Pat. No. 2,967,410. Means are also provided for automatically increasing and decreasing the amount of refrigerant added to the case according to the load on the motor so that the amount of cooling will vary correspondingly with the varying loads on the compressor and thereby maintain the motor continuously at a safe operating temperature. The means for varying the amount of refrigerant injected in the discharge flow may, as provided in both of the above patents, be an aspirating device arranged in the compressor discharge passageway.
It has been recognized in the art that optimum operation of heat pumps on the cooling cycle, i.e., when the indoor heat exchanger is being used as an evaporator, requires a greater effective charge of refrigerant than that required for operation of the heating cycle, when the indor coil is functioning as the condenser. Accordingly, many attempts have been made to solve this problem. U.S. Pat. No. 3,110,164--Smith discloses one of the prior art systems emloyed for accumulating a portion of the refrigerant charge during the heating cycle and for restoring the accumulated portion of the charge to the system during the cooling cycle.